Central banks have never been able to prevent bear markets. Never.

“When there is a boom and everyone is scrambling for common stocks, take all your stocks and sell them. Put the proceeds in the bank [T-bills]. No doubt, the stocks you sold will go higher. Pay no attention to this—just wait for the recession which will come sooner or later. When it gets bad enough to arouse the politicians to make speeches, take your money out of the bank [T-bills] and buy back the stocks. No doubt the stocks will go still lower. Again pay no attention. Wait for the next boom. Continue to repeat this operation as long as you live, and you’ll have the pleasure of dying rich.” –Fred Schwed, Jr., (1940) Where Are the Customers’ Yachts?